128 VAEIABLE STARS IN SOUTHERN HEMISPHERE, 



the most, if not the most remarkable, in the whole heavens. It 

 cannot be expected that this -department of the science can receive 

 many accessions at the hands of professional Astronomers in this 

 Hemisphere, they being too much occupied with the advance- 

 ment of standard astronomy to devote much time to the search 

 for variable stars. It is, however, a department in which a great 

 deal might be done by amateurs. Intelligent persons, even if 

 unprovided with instrumental means, might, by means of good 

 eyes, work with considerable advantage, so far as the observa- 

 tion of stars from the first to the fifth magnitude is concerned. 

 Observation of fainter stars will, of course, require telescopic aid, 

 and it sometimes happens that a star, which at its maximum is a 

 brilliant object to the naked eye, dwindles to a telescopic object 

 as it advances towards its minimum. But telescopes of three or 

 four inches aperture would be of great assistance, and these are 

 within the means of many amateurs. I shall now treat of my 

 subject under three different heads, namely : 



I. The observation of particular stars known to be variable. 



II. The examination of stars suspected to be variable. 



III. A general survey and comparison of all the stars of the 

 Southern Hemisphere. 



And first, the observation of Stars known to be variable. 

 This course of observation should be pursued in order to deter- 

 mine with increased accuracy the law or progress of increase and 

 decrease of their lustre, together with the exact epochs of their 

 maxima and minima. Mr. Pogson, the present director of the 

 Madras Observatory, who has hitherto taken much interest in 

 this department of Astronomy, forwards periodically to the 

 AstronomiscJie Nachrichten ephemerides of the observed variable 

 stars to assist observers in their researches. We must not infer 

 from the fact of a star being observed to go through its varia- 

 tions in a certain period that it will continue to do so. Some of 

 the stars that were originally thought to undergo fluctuations of 

 brightness in regular periods have been found from continuous 

 observation to go through those variations in irregular intervals 

 of time. Thus I may instance the case of the distinguished star 

 Algol in the constellation Perseus, From careful continuous 



